An LTE standardized by 3GPP that is a standard-setting organization for a mobile communication system is a next generation radio communication system that achieves communications with a higher speed and a larger capacity compared with currently operated 3rd and 3.5th generation radio communication systems. Technical specifications of the LTE have been determined with a 3GPP Release 8. Recently, a Release 9 that is a function improved version of the Release 8 and an LTE Advanced that is an upgraded version of the LTE have been studied.
In the LTE Release 9, standardization of detail functions and requirements of a small cell base station (Home eNodeB) are under development. The small cell base station is a small base station capable of being installed in a room and is configured to form a cell (referred to as small cell) which is a communication area having a radius of several to several tens of meters. The small cell base station is installed to disperse the traffic of a large cell base station (Macro eNodeB) configured to form a large cell which is a communication area having a radius of about several hundreds of meters and to cover a dead area in the large cell.
In such a radio communication system, interference may occur in radio communications of a radio terminal connected to the large cell base station due to radio communications of the small cell base station in the following case. Specifically, this occurs when a frequency band of a resource block that is a radio resource capable of being allocated to the radio terminal in the large cell base station partly or completely overlaps with a frequency band of a resource block that is a radio resource capable of being allocated to another radio terminal in the small cell base station. To avoid the interference, for example, Non-Patent Document 1 proposes a technique in which an interface is established between the large cell base station and the small cell base station, and a resource block to be allocated (used) by the small cell base station is restricted by the large cell base station through transmitting a predetermined message to the small cell base station.